Process for making hardenable copper alloy products

ABSTRACT

A METHOD OF IMPROVING THE PROPERTIES OF HEAT HARDENABLE COPPER ALLOYS BY HEATING THE ALLOY IN ITS ORIGINAL CAST FORM TO ITS SOLUTION ANNEALING TEMPERATURE, WORKING THE HEATED ALLOY TO A SELECTED SEMI-FINISHED CROSS SECTION AND IMMEDIATELY THEREAFTER QUENCHING THE ALLOY IN ITS WORKED FORM TO THEREBY OBTAIN A FINE GRAIN STRUCTURE GIVING RISE TO IMPROVED MECHANICAL AND ELECTRICAL PROPERTIES.

United States Patent O 3,717,511 PROCESS FOR MAKING HARDENABLE COPPERALLOY PRODUCTS Hans-Joachim Wallbaum, Osnabruck, Germany, assignor toKabelund Metallwerke Gutehoifnungnutte Aktiengesellschaft, Hannover,Germany No Drawing. Filed Aug. 14, 1968, Ser. No. 752,499 Claimspriority, application Germany, Aug. 16, 1967, P 15 58 790.3 Int. Cl.C22f 1/08 U.S. Cl. 148-115 R 1 Claim ABSTRACT OF THE DISCLOSURE A methodof improving the properties of heat hardenable copper alloys by heatingthe alloy in its original cast form to its solution annealingtemperature, working the heated alloy to a selected semi-finished crosssection and immediately thereafter quenching the alloy in its workedform to thereby obtain a fine grain structure giving rise to improvedmechanical and electrical properties.

BACKGROUND OF THE INVENTION Copper alloys having a small zirconiumcontent of the order of 0.1 to 5.0% have been heated to temperatures inthe range of from 700 to 1000 C., at which temperature the alloy issolution annealed, the heated alloy then being quenched.

Also, it has been suggested that copper-zirconium alloys having azirconium content of the order of 0.01 to 0.15% be quenched aftersolution annealing, followed by cold working to reduce the crosssectional area thereof. Such alloys are suitable as conducting elementssuch as commutator segments in electric motors where optimum mechanicalstrength of the material perpendicular to the direction of forming thematerial is important. However, for semi-finished materials such asrods, wires, etc., such a procedure is without advantage, since theordinate of the perpendicular direction cannot be clearly defined.

Accordingly, an object of this invention is to provide an improvedprocedure for making semi-finished materials from hardenable copperalloys wherein the cast alloy in its heated condition is brounght to itssolution annealing temperature and at such temperature the alloy isWorked to reduce the cross sectional area thereof to a desired form andimmediately thereafter is quenched.

Another object of this invention is to provide a procedure of thecharacter described wherein the heating of the alloy to effect solutionof the alloying constituents is also used in the working of formingoperation, to thereby reduce manufacturing costs and to improve thequality of the product as by producing a fine grain structure, ratherthen the coarse grain structure produced when hot pre-formed material isseparately solution-annealed.

A further object of this invention is to provide a procedure of thecharacter described wherein the immediate quenching of the hot materialafter it has been worked in the hot state, is effective to eliminateoxygen absorption along the surface of the metal. Such oxygen absorptionleads to embrittlement of the skin surface when exposed to hydrogen atelevated temperatures, as in a brazing operation, unless the outer layeris later removed in a separate machining operation.

Still another object of this invention is to provide a procedure of thecharacter described whereinafter the quenching step, to further treatthe alloy product in successive heat hardening, cold-forming andadditional heat hardening steps. Thus, with such procedures, one mayachieve maximum electrical conductivity with maximum tensile strengthand hardness.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the instantinvention is useful for making roller electrodes used for electricresistance welding. An alloy for such purpose consists of 0.6% chromiumwith the balance copper. The rollers are made from cast billets orcompressed rod material and are hot compressed when the material hasbeen heated to its solution-annealing temperature. The resultant discsare quenched immediately after hot compression. The rollers show aconstant fine grain structure across the entire cross-section of thematerial with grain sizes of 25-60 microns. The article also exhibits asubstantial increase in hardness.

In the manufacture of semi-conductor systems and particularly in thecase of base members for carrying the semi-conductors which must showgood mechanical strength, good conductivity and non-porosity; it isadvantageous to utilize a billet of a well known copper-zirconium alloy.Such billet is brought by inductive heating to its solution-annealingtemperature and is then isothermically extruded to form rods which areimmediately thereafter quenched in water.

Thus, the individual steps of solution-annealing and quenching arecombined with the hot forming of the cast metal to obtain the desiredproperties. Such procedure avoids coarse grain structure and a reductionin quality.

Typical heat hardenable copper alloys which may be used with the processof the instant invention, include:

(1) a copper-chromium-zirconium alloy having a content of 0.6% chromium;0.1% zirconium, with the balance copper. The solution annealingtemperature is above 950 C.

(2) a copper-Zirconium alloy having a content of 0.15% zirconium,balance copper. The solution annealing temperature is above 800 C.

(3) a copper-nickel-s-ilicon alloy having a content of 1.3% nickel; 0.5%silicon, balance copper. The solution annealing temperature is above 750C.

(4) a copper-cobalt-bery1lium alloy having a content of 2.5% cobalt;0.6% beryllium, balance copper. The solution annealing temperature isabove 880 C.

It is understood that the essential steps of the process of the instantinvention, as set forth above, may be followed successively by heathardening, cold forming, and a second heat hardening step. Also, suchsteps may be followed by a cold hardening step.

I claim:

1. A method of converting a heat hardenable copper alloy to asemi-finished form, said alloy consisting of copper and a metaladditive, said additive being zirconium in the amount of 0.1% to 5.0% byweight, comprising heating said alloy in its cast state to itssolution-annealing temperature, immediately working the heated alloy toa predetermined semi-finished form of reduced cross sectional area, andimmediately thereafter quenching the same.

(References on following page) 3 4 References Cited 2,225,339 12/1940Harrington 14s -12.1 2,275,188 3/1942 Harrington 14s-12.7 1729 208SCZATES PATENTS 148 127 2,286,734 6/1942 Harrington 148---12.7 e r8011 2,935 4/150 .5 1,992,325 2/1935 Schaarwfichter 148-12.? 504 9 148 112,075,509 3/1937 D vi et 5 WAYLAND w. STALLARD, Primary Examiner2,123,629 7/1938 Hensel et a1. 148-12.7

2,126,827 8/1938 Smith 14812.7 US. Cl. X.R. 2,257,708 9/1941 Stott148-12.7 148--12.7

